JP6540728B2 - Evaporative fuel processing system of engine - Google Patents

Description

  The present invention relates to an evaporative fuel processing apparatus for an engine having an engine body in which cylinders are formed, an intake passage for introducing intake air into the engine body, and a fuel tank for storing fuel.

  BACKGROUND Conventionally, it has been practiced to introduce evaporative fuel generated in a fuel tank into an engine body through an intake passage for combustion, thereby suppressing the evaporative fuel from being released to the atmosphere.

  Here, when the evaporative fuel is simply introduced into the engine main body, the equivalence ratio in the engine main body, that is, in the cylinder deviates from the required value by the evaporative fuel being added to the fuel injected from the fuel injection valve to the engine main body. Therefore, desired engine torque and desired exhaust gas performance can not be obtained.

  On the other hand, Patent Document 1 sets the amount of purge gas, which is a gas introduced into the engine main body, containing the evaporative fuel generated in the fuel tank to be smaller as the engine torque is smaller, and An engine is disclosed that performs feedback control of the injection amount of the fuel injection valve so that the air-fuel ratio of the exhaust passage becomes a target air-fuel ratio corresponding to the required engine torque using the detection value of the provided air-fuel ratio sensor ing.

Japanese Examined Patent Publication 7-3211

  However, in the configuration of Patent Document 1, the amount of purge gas can be reduced to a small amount under operating conditions where the engine torque is small. Therefore, a large amount of evaporated fuel remains in the fuel tank, and there is a possibility that the leakage of the evaporated fuel to the atmosphere can not be sufficiently suppressed.

  On the other hand, for example, it is conceivable to introduce a large amount of evaporative fuel into the intake passage regardless of engine torque, but if the evaporative fuel introduced into the intake passage is rapidly increased, the equivalent ratio in the intake passage and cylinder will be It is desirable to gradually increase the amount of evaporated fuel introduced into the intake passage, because the engine torque fluctuates due to sudden changes. However, if the amount of evaporative fuel is simply increased by a fixed amount, when the amount of air flowing through the intake passage changes, the equivalence ratio of the gas in the intake passage changes accordingly. There is a possibility that the equivalence ratio of the gas inside may fluctuate and deviate from an appropriate value.

  The present invention has been made in view of the above-described circumstances, and can appropriately control the equivalence ratio in the cylinder while suppressing the leakage of the evaporative fuel generated in the fuel tank into the atmosphere. An object of the present invention is to provide an evaporative fuel processing system for an engine.

In order to solve the above problems, the present invention is an evaporative fuel processing apparatus of an engine having an engine body in which cylinders are formed, an intake passage for introducing intake air into the engine body, and a fuel tank for storing fuel. A purge passage connected to the intake passage for introducing a purge gas containing evaporated fuel evaporated in the fuel tank into the intake passage, a purge valve capable of opening and closing the purge passage, and control means for controlling the purge valve The control means controls the purge valve to increase an intake manifold equivalent ratio, which is an equivalent ratio of gas in the intake passage, at the time of performing purge for introducing the purge gas into the intake passage. control with implementing, in the increase Daisei during your implementation, estimates the current intake manifold equivalence ratio, and, flowing through the intake passage After the increase correction amount of the intake manifold equivalent ratio is calculated based on the latest change amount of the air volume, the target intake manifold equivalent ratio is calculated by adding the increase correction amount to the estimated intake manifold equivalent ratio, and An evaporative fuel processing system for an engine, comprising: controlling the purge valve so that an intake manifold equivalent ratio becomes the target intake manifold equivalent ratio (claim 1).

  According to the present invention, by controlling the opening degree of the purge valve so that the intake manifold equivalent ratio increases, it is possible to suppress a sudden change of the equivalent ratio of the gas in the cylinder, and the intake manifold equivalent ratio is increased. By controlling the purge valve so as to achieve a predetermined target value, it is possible to make the intake manifold equivalent ratio, that is, the equivalent ratio of the gas before being introduced into the cylinder more appropriately to an appropriate value. Therefore, the equivalent ratio of the gas in the cylinder can be appropriately controlled to improve the engine torque and the exhaust gas performance.

  Moreover, the increase correction amount is calculated based on the amount of change in the amount of air flowing through the intake passage, and this is added to the current intake manifold equivalent ratio (estimated value) to achieve the target intake manifold equivalent value which is the target value of the intake manifold equivalent ratio. The ratio is calculated. Therefore, the intake manifold equivalent ratio can be controlled to a more appropriate value.

  Specifically, if the purge valve is controlled such that the intake manifold equivalent ratio becomes the target value as described above, the equivalent ratio of the gas in the cylinder can be made appropriate. However, if the purge valve is controlled such that the target intake manifold equivalent ratio is simply increased by a fixed value from the current intake manifold equivalent ratio regardless of changes in the amount of air flowing through the intake channel, the intake passage When the amount of flowing air changes with acceleration and deceleration, the change in intake manifold equivalent ratio caused by the change in the amount of air is not added, and the target intake manifold equivalent ratio is set. Therefore, the target intake manifold equivalent ratio is not properly set, and the intake manifold equivalent ratio is not controlled to an appropriate value.

  On the other hand, in the present invention, the increase correction amount is calculated based on the change amount of the air amount flowing through the intake passage, and this is added to the current intake manifold equivalent ratio to calculate the target intake manifold equivalent ratio. Therefore, the target intake manifold equivalent ratio can be set to an appropriate value corresponding to the change in the amount of air, and the intake manifold equivalent ratio can be appropriately controlled.

  In the above configuration, the control means sequentially increases or decreases the amount of air flowing through the intake passage to a basic increase correction amount determined in advance so as to increase as the amount of air flowing through the intake passage increases. It is preferable to calculate what added the amount as said increase correction amount (Claim 2).

  In this way, the target intake manifold equivalent ratio, that is, the actual intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder are controlled to appropriate values according to the amount of air flowing through the intake passage itself and the amount of change in the amount of air. can do.

  In the above configuration, the control means sets the successive correction amount to a value larger than 0 when the latest change amount of the air amount flowing through the intake passage is larger than 0, and the latest change of the air amount. When the amount is smaller than 0, it is preferable to set the successive correction amount to a value smaller than 0 (claim 3).

  According to this configuration, the amount of air flowing through the intake passage increases with the acceleration of the engine and the like, whereby the increase correction amount is set to a value larger than 0 even if the intake manifold equivalent ratio becomes smaller. The ratio can be maintained at a high value, and the target is achieved by setting the amount of increase correction to a value smaller than 0 even if the intake manifold equivalent ratio is increased due to the decrease in the amount of air as the engine decelerates, etc. The intake manifold equivalent ratio can be prevented from becoming excessively large relative to the current intake manifold equivalent ratio, and the target intake manifold equivalent ratio and thus the actual intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder can be appropriately controlled.

  In the above configuration, a fuel injection valve for injecting fuel into the cylinder or the intake passage is provided, and the control means is a reference target fuel that is a target value of the total fuel amount supplied to the engine body based on the operating state of the engine body. At the start of the purge, the target maximum purge fuel amount is calculated by setting the amount and subtracting the minimum value of the injection amount of the fuel injection valve that ensures the linearity characteristic of the fuel injection valve from the reference target fuel amount. The increase control is performed until the amount of evaporative fuel introduced into the engine main body through the purge passage reaches the target maximum purge fuel amount, and the evaporative fuel introduced into the engine main body through the purge passage Preferably, the fuel injection valve is injected with an amount of fuel obtained by subtracting the amount of fuel from the reference target fuel amount (claim 4).

  According to this configuration, the reference target fuel amount is realized by the fuel supply from the fuel injection valve to the engine body and the fuel supply to the engine body by the purge while appropriately controlling the equivalence ratio in the cylinder by the execution of the increase control. Engine torque can be maintained at an appropriate value, and a large amount of evaporative fuel is introduced into the engine body while maintaining the linearity characteristic of the fuel injection valve to suppress the evaporative fuel leakage from the fuel tank to the atmosphere it can.

  As described above, it is possible to appropriately control the equivalence ratio in the cylinder while suppressing the leakage of the evaporative fuel generated in the fuel tank into the atmosphere.

FIG. 1 is a schematic view of an engine system to which an evaporative fuel processing device for an engine according to an embodiment of the present invention is applied. It is a block diagram showing a control system of an engine system. It is the flowchart which showed the control procedure of the purge valve. It is the flowchart which showed the first half part of calculation procedure of target purge mass flow. It is the flowchart which showed the second half part of calculation procedure of target purge mass flow. It is the flowchart which showed the control procedure of the injector. It is the figure which showed typically the relationship between the amount of air change, the target intake manifold equivalent ratio, and the present intake equivalent ratio. It is the figure which showed the relationship between the injection pulse width and the injection quantity. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of acceleration in this embodiment, and the amount of intake manifold air. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of acceleration in a comparative example, and the amount of intake manifold air. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of deceleration in this embodiment, and the amount of intake manifold air. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of deceleration in a comparative example, and the amount of intake manifold air.

(1) Overall Configuration of Engine FIG. 1 is a view showing the configuration of an engine system to which an evaporative fuel processing system for an engine according to an embodiment of the present invention is applied. The engine system of this embodiment includes a four-stroke engine body 1, an intake passage 30 for introducing combustion air (intake air) to the engine body 1, and an exhaust gas for discharging exhaust gas from the engine body 1 to the outside. A passage 35, a fuel tank 41 for storing fuel, and a purge system 40 for introducing evaporative fuel generated in the fuel tank 41 into the engine body 1 are provided. The engine system is provided in a vehicle, and the engine body 1 is used as a drive source of the vehicle. The engine main body 1 is, for example, a four-cylinder engine having four cylinders 2 aligned in a direction perpendicular to the paper surface of FIG. 1 and is a gasoline engine that mainly uses gasoline as a fuel.

  The engine body 1 has a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston 11 reciprocably inserted in the cylinder 2 There is. A combustion chamber 5 is formed above the piston 11.

  The piston 11 is connected to the crankshaft 15 via a connecting rod, and in response to the reciprocation of the piston 11, the crankshaft 15 rotates about a central axis. The cylinder block 3 is provided with a rotation number sensor SN1 that detects the rotation number of the crankshaft 15 as the rotation number of the engine.

  The cylinder head 4 is provided with an injector 12 and an ignition plug 13 for igniting the mixture of fuel and air injected from the injector 12 by spark discharge, one for each cylinder 2.

  The injector 12 has a plurality of injection holes serving as a fuel injection port at its tip, and is provided so as to face the combustion chamber 5 of each cylinder 2 from the side of the intake side thereof. A fuel rail 14 storing fuel inside is connected to the injector 12. The fuel rail 14 is connected to the fuel tank 41 via a pipe (not shown). The fuel rail 14 stores the fuel pressure-fed from the fuel tank 41. The injector 12 receives the supply of the fuel stored in the fuel rail 14 and injects the fuel into the cylinder 2.

  The fuel rail 14 is provided with a fuel pressure sensor SN5 for detecting the pressure of the fuel stored in the fuel rail 14, that is, the pressure of the fuel injected by the injector 12.

  The spark plug 13 has an electrode at its tip end for discharging a spark, and is provided to face the combustion chamber 5 of each cylinder 2 from above.

  The cylinder head 4 includes an intake port 6 for introducing air supplied from the intake passage 30 into the combustion chamber 5 of each cylinder 2, an intake valve 8 for opening and closing the intake port 6, and a combustion chamber 5 of each cylinder 2. An exhaust port 7 for leading the exhaust generated in the above to the exhaust passage 35 and an exhaust valve 9 for opening and closing the exhaust port 7 are provided.

  The intake passage 30 includes a single intake pipe 33, and a plurality of (four) independent intake paths 31 (which are orthogonal to the sheet of FIG. 1) individually connecting the intake pipe 33 and the intake port 6 of each cylinder 2. Side by side in the direction). A surge tank 32 having a predetermined volume is provided at the downstream end of the intake pipe 33, and an independent intake passage 31 extends from the surge tank 32 to each intake port 6, respectively.

  A throttle valve 34 capable of opening and closing the passage of the intake pipe 33 is provided at a portion of the intake pipe 33 upstream of the surge tank 32.

  An air flow sensor SN2 is provided at a portion of the intake pipe 33 upstream of the throttle valve 34 for detecting the flow rate of air taken into the engine body 1 through this portion. The surge tank 32 is provided with an intake pressure sensor SN3 for detecting the pressure in the surge tank 32, that is, the pressure of a portion of the intake pipe 33 downstream of the throttle valve 34.

  The exhaust passage 35 is provided with a catalyst device 90 in which a catalyst such as a three-way catalyst is incorporated. Further, the exhaust passage 35 is provided with an A / F sensor SN4 for detecting the exhaust gas, that is, the air-fuel ratio (ratio of air to fuel) of the mixture of air and fuel in the combustion chamber 5.

  The purge system 40 includes a canister 42 for detachably adsorbing evaporated fuel evaporated in the fuel tank 41, a purge air pipe 49 for introducing air into the canister 42, and a purge pipe for connecting the canister 42 and the intake pipe 33 (purge Passage 43). The purge pipe 43 is connected to a portion of the intake pipe 33 between the throttle valve 34 and the surge tank 32.

  The evaporated fuel adsorbed to the canister 42 is desorbed from the canister 42 by the air introduced from the purge air pipe 49. The evaporated fuel desorbed from the canister 42 is introduced into the intake pipe 33 through the purge pipe 43 together with air. Hereinafter, a gas composed of the evaporated fuel and air flowing through the purge pipe 43 is referred to as a purge gas. Further, the evaporated fuel contained in the purge gas is referred to as a purge fuel.

  The purge pipe 43 is provided with a purge valve 45 for opening and closing the purge pipe 43. The purge valve 45 is a DUTY control valve, and is repeatedly opened and closed to change the duty ratio, which is the ratio of the valve opening period to the unit period including one valve opening period and the valve closing period. Is supposed to be changed. The purge valve 45 is an electromagnetic valve, and the duty ratio is a ratio of an energization period to a unit period obtained by combining one energization period and one non-energization period. The purge valve 45 is fully closed at a duty ratio of 0% and fully open at 100%.

  Hereinafter, the operation of opening the purge valve 45 and introducing the purge gas into the intake pipe 33 and the respective cylinders 2 is referred to as “purge” or “purge”.

(2) Control System The control system of the engine system will be described with reference to FIG. The engine system of the present embodiment is controlled by a PCM (power train control module) 100 mounted on a vehicle. The PCM 100 is a microprocessor including a CPU, a ROM, a RAM, an I / F, and the like, and corresponds to the control means according to the present invention.

  Information from various sensors is input to the PCM 100. For example, the PCM 100 is electrically connected to the rotation speed sensor SN1, the air flow sensor SN2, the intake pressure sensor SN3, the A / F sensor SN4, and the fuel pressure sensor SN5, and receives input signals from these sensors SN1 to SN5. The vehicle is further provided with an accelerator opening sensor SN6 for detecting the opening of an accelerator pedal (not shown) operated by the driver, a vehicle speed sensor SN7 for detecting the vehicle speed, etc. These sensors SN6 and SN7 The detection signal according to is also input to the PCM 100. The PCM 100 executes various calculations and the like based on input signals from the respective sensors (SN1 to SN7, etc.) to drive the injector 12, the purge valve 45 (actuator for driving the purge valve 45), the throttle valve 34 (the throttle valve 34). Outputs command signals to control the actuator and the like.

  The PCM 100 has an injector control unit 102 and a purge valve control unit 104 as functional elements. The injector control unit 102 performs an operation related to the injector 12, calculates an injection amount or the like which is a fuel amount injected from the injector 12 to the cylinder 2, and outputs a signal corresponding thereto to the injector 12. The purge valve control unit 104 performs an operation related to the purge valve 45, calculates a command value of the duty ratio of the purge valve 45 (hereinafter referred to as a purge valve command duty ratio as appropriate), and outputs a signal corresponding thereto to the purge valve 45. Each of the control units 102 and 104 performs an operation at predetermined time intervals and outputs a signal to each unit.

(Purge valve control procedure)
The control procedure of the purge valve 45 will be described with reference to FIGS. 3, 4 and 5.

  As shown in FIG. 3, the PCM 100 first reads detection values of the sensors SN1 to SN7 and the like.

  Next, in step S2, a target intake amount is calculated. The target intake air amount is a mass flow rate of air to be supplied to the engine body 1 (specifically, to be supplied to each cylinder 2). The PCM 100 calculates a required torque which is a torque required of the engine body 1 based on the accelerator opening degree and the vehicle speed, etc., and calculates and calculates the filling efficiency of the cylinder 2 necessary to realize the required torque. The target intake air amount is calculated based on the charging efficiency and the engine speed.

  Next, in step S3, a cylinder required fuel amount (reference target fuel amount) Qcyl is calculated based on the operating state of the engine body. The cylinder required fuel amount Qcyl is the total amount of fuel to be supplied to the engine body 1 (specifically, to be supplied to each cylinder 2). The PCM 100 calculates the cylinder required fuel amount Qcyl based on the charging efficiency calculated as described above, the engine speed, and the like.

  Next, in step S4, it is determined whether a purge execution condition which is an operation condition for executing the purge is satisfied. For example, when fuel cut is performed, it is determined that the purge execution condition is not satisfied.

  If the determination in step S4 is NO and the purge execution condition is not satisfied, the process proceeds to step S5 to stop the purge, and the target value of the volumetric flow rate of the purge gas introduced to the engine main body 1 (each cylinder 2) The target purge volumetric flow rate is set to 0, and the process proceeds to step S10.

  On the other hand, if the determination in step S4 is YES and the purge execution condition is satisfied, the process proceeds to step S6.

  In step S6, the minimum injection amount Qinj_min is set. The minimum injection amount Qinj_min is the minimum value of the injection amount of the injector 12 in which the linearity characteristic of the injector 12 is secured. Specifically, under the condition that the fuel pressure is constant, the injection amount of the injector 12 basically increases or decreases in proportion to the command value. However, as shown in FIG. 8 in which the horizontal axis represents the injection pulse width, ie, the injection period corresponding to the command value of the injection amount, and the vertical axis represents the actual injection amount, in the region A1 where the injection amount is less than the predetermined amount The injection amount is proportional to the injection pulse width only in the region A2 where the injection amount is not less than the predetermined amount, and the minimum injection amount Qinj_min is the predetermined amount.

  Here, the minimum injection amount Qinj_min varies with the fuel pressure. Therefore, in step S6, the minimum injection amount Qinj_min is set based on the fuel pressure. In the present embodiment, the relationship between the fuel pressure and the minimum injection amount Qinj_min is obtained in advance in experiments and the like in the PCM 100 and stored in a table, and the PCM 100 calculates the value corresponding to the current fuel pressure from this table as the minimum injection amount. Extract as Qinj_min.

  Next, in step S7, a target maximum purge fuel amount Qpurge_max is calculated. The target maximum purge fuel amount Qpurge_max is the amount of purge fuel that can be supplied to the engine main body 1 (each cylinder 2) while securing the linearity characteristic of the injector 12 and making the output torque of the engine main body 1 the required torque. The maximum value is calculated by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl.

  Next, in step S8, the target purge mass flow rate is calculated using this target maximum purge fuel amount Qpurge_max.

  FIGS. 4 and 5 are flowcharts showing the procedure for calculating the target purge mass flow rate.

  As shown in FIG. 4, the PCM 100 first calculates a target maximum intake manifold equivalent ratio based on the target maximum purge fuel amount Qpurge_max and the like in step S21. The intake manifold equivalent ratio is the equivalent ratio of the gas in the intake passage 30, and the equivalent ratio of the mixed gas of the air introduced into the intake passage 30 from the outside of the engine system and the purge gas introduced into the intake passage 30 from the purge pipe 43. It is. Specifically, the intake manifold equivalent ratio is an equivalent ratio of the gas in the intake pipe 33 immediately before being introduced into the cylinder 2. The target maximum intake manifold equivalent ratio is an intake manifold equivalent ratio which is estimated to be realized when the purge fuel for the target maximum purge fuel amount Qpurge_max is introduced into the intake pipe 33.

  Specifically, the PCM 100 is required to introduce the purge fuel for the target maximum purge fuel amount Qpurge_max into the intake pipe 33 from the target maximum purge fuel amount Qpurge_max and the fuel concentration of the purge gas (hereinafter referred to as the purge gas concentration). A mass flow rate of the purge gas is calculated, and a target maximum intake manifold equivalent ratio is calculated from a gas amount obtained by combining the mass flow rate of the purge gas and the mass flow rate of air detected by the air flow sensor SN2 and a target maximum purge fuel amount Qpurge_max. The calculation procedure of the purge gas concentration will be described later.

  In this embodiment, when purge is started, the intake manifold equivalent ratio is increased toward the target maximum intake manifold equivalent ratio, and the target intake manifold equivalent ratio (i is a target value of each time of the intake manifold equivalent ratio). ) Is calculated to be gradually increased toward the target maximum intake manifold equivalent ratio. As described above, the purge valve control unit 104 performs the calculation every predetermined time, and calculates the target intake manifold equivalent ratio every time.

  In step S22, the current value of the amount of air in the intake manifold 33, i.e., the amount of air immediately before being introduced into the cylinder 2 among the air in the intake pipe 33, is estimated. Do.

  In the present embodiment, the current intake manifold air amount (i) is estimated using the detection value of the intake pressure sensor SN3, the detection value of the air flow sensor SN2, and the like. Here, i is a counter indicating the number of operation cycles. After step S22, the process proceeds to step S23.

  In step S23, the present intake manifold equivalent ratio (i) is estimated.

  In the present embodiment, the current intake manifold equivalent is obtained using the mass flow rate of the purge gas calculated based on the current intake air amount (i) calculated in step S22, the purge gas concentration, the duty ratio of the purge valve 45 as described later, etc. Estimate ratio (i).

  Next, in step S24, a basic increase correction amount F (i) used to calculate the target intake manifold equivalent ratio (i) is calculated as described later. The basic increase correction amount F (i) is set to a value larger than zero. Further, in the present embodiment, the basic increase correction amount F (i) is calculated based on the current intake air amount (i), and is set to a larger value as the current intake air amount (i) is larger.

  Next, at step S25, an air change amount ΔQa (i) which is a change amount of the amount of intake air is calculated. Specifically, air change amount ΔQa is a value obtained by subtracting the previous intake manifold air amount (i-1), that is, the intake manifold air amount calculated one operation cycle before from the intake manifold air amount (i) calculated in step S22. (I)

  Next, in step S26, it is determined whether the air change amount ΔQa (i) calculated in step S25 is zero. That is, it is determined whether the operating state of the engine is a steady state and the intake manifold air amount is maintained at a constant value. In step S26, it is not necessary to determine whether the air change amount ΔQa (i) is strictly 0 or not, and whether the air change amount ΔQa (i) is substantially 0, that is, It may be determined whether the amount of air in the intake manifold has substantially changed. Therefore, for example, in step S26, it may be determined whether the absolute value of the air change amount ΔQa (i) is smaller than a predetermined value larger than zero.

  If the determination in step S26 is YES and the air change amount ΔQa (i) is 0 and the intake air amount is maintained constant, the process proceeds to step S27.

  In step S27, a value obtained by adding the basic increase correction amount F (i) calculated in step S24 to the current intake manifold equivalent ratio (i) calculated in step S23 is set as the target intake manifold equivalent ratio (i). After step S27, the process proceeds to step S32.

  On the other hand, if the determination in step S26 is NO, and the air change amount ΔQa (i) is not 0 but the intake manifold air amount is changing, the process proceeds to step S28. For example, at the time of acceleration of the vehicle and the engine, the intake manifold air amount increases, and the air change amount ΔQa (i) becomes a value larger than 0, and the determination in step S26 is NO. Further, at the time of deceleration of the vehicle and the engine, the intake manifold air amount decreases, the air change amount ΔQa (i) becomes a value smaller than 0, and the determination of step S26 becomes NO.

  In step S28, the sequential correction amount G (i) used to calculate the target intake manifold equivalent ratio (i) is calculated based on the air change amount ΔQa (i) as described later. The sequential correction amount G (i) is set to a larger value as the air change amount ΔQa (i) is larger. Then, if the air change amount ΔQa (i) is larger than 0, the correction amount G (i) is sequentially set to a value larger than 0, and if the air change amount ΔQa (i) is smaller than 0, one by one The correction amount G (i) is also set to a value smaller than zero. For example, the correction amount G (i) is calculated by multiplying the air change amount ΔQa (i) by a predetermined coefficient (> 0).

  After step S28, the process proceeds to step S29. In step S29, a value obtained by adding the basic increase correction amount F (i) and the correction amount G (i) successively to the current intake manifold equivalent ratio (i) is set as the target intake manifold equivalent ratio (i).

  After step S29, the process proceeds to step S30. In step S30, it is determined whether the target intake manifold equivalent ratio (i) calculated in step S29 is smaller than the previous target intake manifold equivalent ratio (i-1). If the determination in step S30 is NO, the process proceeds to step S32.

  On the other hand, if the determination in step S30 is YES and the target intake manifold equivalent ratio (i) is smaller than the previous target intake manifold equivalent ratio (i-1), the process proceeds to step S31. Then, in step S31, the target intake manifold equivalent ratio (i) is maintained at the previous target intake manifold equivalent ratio (i-1), and the process proceeds to step S32.

  As shown in FIG. 5, in step S32, it is determined whether the target intake manifold equivalent ratio (i) calculated as described above is equal to or higher than the target maximum intake manifold equivalent ratio calculated in step S21.

  When the determination in step S32 is NO and the target intake manifold equivalent ratio (i) is less than the target maximum intake manifold equivalent ratio, the process proceeds to step S34.

  On the other hand, if the determination in step S32 is YES and the target intake manifold equivalent ratio (i) is equal to or higher than the target maximum intake manifold equivalent ratio, the process proceeds to step S33. Then, in step S33, the target intake manifold equivalent ratio (i) is set to the target maximum intake manifold equivalent ratio (i). After step S33, the process proceeds to step S34.

  In step S34, a target purge mass flow rate is calculated based on the target intake manifold equivalent ratio (i). The target purge mass flow rate (i) is the mass flow rate of the purge gas necessary to realize the target intake manifold equivalent ratio (i), and the target intake manifold equivalent ratio (i) and the air flow rate and purge gas concentration detected by the air flow meter Calculated based on After step S34, the process proceeds to step S9 shown in FIG.

  In step S9, the target purge mass flow rate (i) is calculated by converting the target purge mass flow rate (i) into a volumetric flow rate based on the temperature and pressure of the purge gas. In the present embodiment, the temperature and pressure of the purge gas are the temperature and pressure of the atmosphere.

  After step S9, the process proceeds to step S10, where a purge valve command duty ratio is calculated based on the target purge volume flow rate (i).

  In the present embodiment, the differential pressure across the purge valve 45 is calculated, and the purge valve command duty ratio is determined based on the differential pressure and the target purge volumetric flow rate.

  Specifically, the pressure loss of the purge pipe 43 is calculated, and a value obtained by subtracting this pressure loss from the atmospheric pressure is used as the pressure on the upstream side of the purge valve 45 of the purge pipe 43, and the intake pressure detected by the intake pressure sensor SN3. The pressure difference between the front and rear of the purge valve 45 is calculated as the pressure downstream of the purge valve 45. Further, the relationship between the differential pressure, the volumetric flow rate of the purge gas, and the duty ratio of the purge valve is set in advance by a map by experiment or the like and stored in the PCM 100, and the PCM 100 calculates the difference before and after the purge valve 45 calculated from this map. The duty ratio corresponding to the pressure and the target purge volume flow is extracted and determined as the purge valve commanded duty ratio.

  As described above, when the determination in step S4 is NO and the process proceeds to step S5 and the target purge volume flow rate is set to 0, the purge valve command duty ratio is 0%.

  After step S10, the process proceeds to step S11. Then, in step S11, a signal of the purge valve command duty ratio set in step S10 is output to the purge valve 45.

  Thus, in the present embodiment, when the purge is started, the target intake manifold equivalent ratio and thus the intake manifold equivalent ratio are increased toward the target maximum intake manifold equivalent ratio. Then, at the time of execution of the increase control to increase this intake manifold equivalent ratio, the total value of the basic increase correction amount F calculated based on the current intake manifold air amount and the sequential correction amount G calculated based on the air change amount ΔQa Is added to the current intake manifold equivalent ratio, and the value is set as the target intake manifold equivalent ratio. Further, the target intake manifold equivalent ratio (i) is maintained at or above the previous target intake manifold equivalent ratio (i-1).

  FIG. 7 is a schematic diagram showing the relationship between the amount of air change ΔQa and the target intake manifold equivalent ratio s and the current intake manifold equivalent ratio u. As shown in FIG. 7, when the air change amount ΔQa is 0, the target intake manifold equivalent ratio s is made larger by the basic increase correction amount F than the current intake manifold equivalent ratio u. Then, when the air change amount ΔQa is larger than 0, that is, at the time of acceleration etc. and the amount of intake manifold air is increasing, the target intake manifold equivalent ratio s is a basic increase correction amount from the current intake manifold equivalent ratio u. After being increased by F, the correction amount G is successively increased. On the other hand, when the air change amount ΔQa is smaller than 0, that is, at the time of deceleration etc. and the intake manifold air amount is decreasing, the target intake manifold equivalent ratio s is the basic increase correction amount from the current intake manifold equivalent ratio u. The value obtained by subtracting the absolute value of the correction amount G sequentially from the value that is larger by F is obtained.

(Injector control procedure)
Next, a procedure for calculating the injection amount of the injector 12 (command injection amount which is a command value of the injection amount of the injector 12) will be described using FIG.

  In step S41, the PCM 100 first reads the cylinder required fuel amount Qcyl calculated in step S3, the purge valve command duty ratio set in step S10, and the like.

  Next, in step S42, the actual purge volumetric flow rate, which is the current value of the volumetric flow rate of the purge gas introduced into the engine body 1, is estimated.

  Specifically, the volume flow rate of the basic purge gas is calculated based on the current duty ratio of the purge valve 45 and the differential pressure across the purge valve 45 calculated in the calculation process of step S10, and then this is used as a purge valve. The volume flow rate of the purge gas is estimated by correcting the voltage supplied to 45, the drive frequency of the purge valve 45 and the temperature around the purge valve 45.

  Next, in step S43, the actual purge volume flow rate calculated in step S42 is converted into a mass flow rate to calculate an actual purge mass flow rate.

  Next, in step S44, an actual purge fuel amount Qpurge_r, which is the amount of purge fuel currently introduced to the engine body 1, is estimated. Specifically, the actual purge fuel amount Qpurge_r is calculated based on the actual purge mass flow rate and the purge gas concentration calculated in step S43.

  Next, in step S45, a value obtained by subtracting the actual purge fuel amount Qpurge_r from the cylinder required fuel amount Qcyl is calculated as a basic injection amount.

  Next, in step S46, the basic injection amount is A / F_feedback corrected to calculate a command injection amount. That is, in this embodiment, the injection amount of the injector 12 is corrected so that the air-fuel ratio of the gas in the exhaust passage 35 detected by the A / F sensor SN4 becomes a preset target value. The basic injection amount is corrected with this correction amount.

  After step S46, the process proceeds to step S47, and the injector 12 is made to inject the command injection amount calculated in step S46.

  As described above, in the present embodiment, the injection amount of the injector 12 is basically set to an amount obtained by subtracting the actual purge fuel amount Qpurge_r, that is, the amount of purge fuel introduced into the engine body 1 from the cylinder required fuel amount Qcyl. Ru.

(Purge concentration estimation procedure)
Next, the procedure for estimating the purge gas concentration will be described.

  In the present embodiment, the purge gas concentration is estimated based on the air-fuel ratio of the gas in the exhaust passage 35 detected by the A / F sensor SN4 under a predetermined operation condition in which the purge is performed. Specifically, the difference between the preset target value of the air-fuel ratio of the exhaust passage 35 and the actual air-fuel ratio detected by the A / F sensor SN4 is supplied by supplying the purge fuel to the engine body 1 As it occurs, the purge gas concentration is estimated based on this deviation amount and the mass flow rate of the purge gas. In the present embodiment, under the predetermined operating conditions, the average value of the deviation amount and the average value of the flow rate of the purge gas are calculated, and the purge gas concentration is estimated using these values.

(3) Operation, Etc. As described above, in the present embodiment, the target intake manifold equivalent ratio and thus the intake manifold equivalent ratio gradually increase toward the target maximum intake manifold equivalent ratio at the time of execution of purge. As a result, the opening degree of the purge valve 45 is changed. Therefore, it is possible to suppress a sudden change of the intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder 2 due to the execution of the purge. Further, the purge valve 45 is controlled so that the intake manifold equivalent ratio becomes a predetermined target value, and the intake manifold equivalent ratio, that is, the equivalent ratio of the gas before being introduced into the cylinder can be more reliably made appropriate The equivalence ratio of the pre-combustion gas in the cylinder 2 can be appropriately controlled. Therefore, engine torque and exhaust gas performance can be improved.

  Moreover, the incremental correction amount G calculated based on the air change amount ΔQa which is the change amount of the intake air amount, that is, the air amount change amount in the intake pipe 33, and the basic increase correction amount F calculated based on the intake air amount The target intake manifold equivalent ratio is calculated by adding the increase correction amount obtained by combining the above with the present intake manifold equivalent ratio. Therefore, while suppressing sudden changes in intake manifold equivalent ratio and equivalent ratio of gas in the cylinder as described above, more purge gas is introduced into the intake pipe 33 to reduce the amount of evaporated fuel remaining in the fuel tank earlier. It can be done.

  Specifically, as described above, if the purge valve is controlled so that the intake manifold equivalent ratio becomes a predetermined target value, the equivalent ratio of the gas in the cylinder can be appropriately controlled. However, for example, when the opening degree of the purge valve is changed so as to simply increase the intake manifold equivalent ratio from the current intake manifold equivalent ratio by a predetermined value, regardless of the amount of air change ΔQa and the amount of intake manifold air. When the amount of intake manifold air changes during acceleration / deceleration etc., the opening degree of the purge valve 45 is changed without taking into account the change in intake manifold equivalent ratio resulting from the change in the amount of intake manifold air. Therefore, the amount of purge fuel introduced into the intake pipe 33 becomes excessive and fluctuation of the equivalence ratio of gas in the cylinder 2 becomes large, or the amount of purge fuel introduced into the intake pipe 33 becomes too small. There is a possibility that the amount of evaporated fuel remaining in the fuel tank 41 can not be sufficiently reduced.

  This will be described in detail with reference to FIGS. 9 to 12. 9 and 10 show target intake manifold equivalent ratio and intake manifold equivalent ratio (the actual intake manifold equivalent ratio, hereinafter referred to as actual intake manifold equivalent ratio) when the amount of intake manifold air increases during engine acceleration etc. And, the time change of the intake manifold air amount is schematically shown. FIG. 11 and FIG. 12 schematically show these time changes when the intake manifold air amount decreases at engine deceleration and the like. Moreover, FIG. 9 and FIG. 11 is a figure when performing control which concerns on this embodiment, FIG. 10 and FIG. 12 are comparative examples, and simply make the intake manifold equivalent ratio the present intake manifold equivalent as mentioned above. It is a figure when changing the opening degree of a purge valve so that only a fixed value may be made to increase from ratio (actual intake manifold equivalent ratio).

  As shown in FIGS. 9 and 10, the actual intake manifold equivalent ratio is substantially controlled to the previously calculated target intake manifold equivalent ratio by changing the opening degree of the purge valve 45 until the intake manifold air amount starts to increase with acceleration at time t3. Be done. For example, in the comparative example shown in FIG. 10, when the target intake manifold equivalent ratio P (t1) is set to a predetermined value at time t1, the opening degree of the purge valve 45 is changed so as to realize this. The actual intake manifold equivalent ratio Q (t2) is set to this predetermined value at t2. Then, the target intake manifold equivalent ratio P and the actual intake manifold equivalent ratio Q appropriately increase until time t3. However, when increase of the intake manifold air amount starts at time t3, along with this, actual intake manifold equivalent ratio Q (t4) does not reach target intake manifold equivalent ratio P (t3) at time t4, and increase of actual intake manifold equivalent ratio The amount is kept small.

  Here, in the comparative example, as described above, the target intake manifold equivalent ratio P is set to a value obtained by adding the constant value α to the actual intake manifold equivalent ratio Q, and the target intake manifold equivalent calculated at time t4. The ratio P (t4), that is, the intake manifold equivalent ratio to be realized at time t5 is a value obtained by adding a constant value α to the actual intake manifold equivalent ratio Q (t4) at time t4. That is, in the comparative example, the increase amount of the target intake manifold equivalent ratio P between time t4 and time t3 substantially matches the increase amount of the actual intake manifold equivalent ratio Q between time t4 and time t3. It is controlled. Therefore, as described above, when the increase amount of actual intake manifold equivalent ratio Q from time t3 is suppressed small at time t4, the increase amount of target intake manifold equivalent ratio P also decreases and the target calculated at time t4. The intake manifold equivalent ratio P (t4) can be kept small. This similarly occurs during time t4 (during an increase in the intake manifold air amount). Therefore, in the comparative example, as shown in FIG. 10, the increase in the target intake manifold equivalent ratio P is suppressed after time t4, and along with this, the actual intake manifold equivalent ratio Q and hence the purge fuel introduced into the intake pipe 33 The amount is not properly increased, and the amount of evaporated fuel remaining in the fuel tank 41 can not be reduced sufficiently.

  On the other hand, as shown in FIG. 9, at time t4 immediately after the increase of the intake air amount starts at time t3, the actual intake manifold equivalent ratio u (t4) is relatively the same as in the comparative example also in this embodiment. It can be reduced to a small value. However, in the present embodiment, the basic increase correction amount F set according to the amount of intake manifold air and the sequential correction amount G set according to the air change amount ΔQa are added to the actual intake manifold equivalent ratio u (t4) As a result, the target intake manifold equivalent ratio s (t4) is calculated. Therefore, the target intake manifold equivalent ratio s (t4) is set to a relatively high value at time t4, and the intake manifold equivalent ratio u (t5) at time t5 is maintained at a high value. Similarly, after time t4, the target intake manifold equivalent ratio s is set to a high value, and the intake manifold equivalent ratio u is increased. Therefore, in the present embodiment, the actual intake manifold equivalent ratio u can be appropriately increased even under operating conditions in which the intake manifold equivalent ratio tends to decrease as the amount of intake manifold air increases, and the purge introduced into the intake pipe 33 The amount of fuel can be increased appropriately to reduce the amount of evaporated fuel remaining in the fuel tank 41 early.

  Further, as shown in FIG. 12, in the comparative example, when deceleration is started at time t3 and the intake manifold air amount decreases, target intake manifold equivalent ratio P (actual intake manifold equivalent ratio Q (t4) should be realized at time t4. It becomes larger than t3). Further, a value obtained by adding a constant value α to the excessive actual intake manifold equivalent ratio Q (t4) is taken as the next target intake manifold equivalent ratio P (t4), so that the next target intake manifold equivalent ratio P (t4) is also It becomes an excessively large value. Therefore, in the comparative example, the increase amounts of the target intake manifold equivalent ratio P and the actual intake manifold equivalent ratio Q become large as compared with the case where there is no change in the amount of intake manifold air indicated by the broken line, that is, steady operation. Therefore, in the comparative example, the amount of increase of the purge fuel introduced into the intake pipe 33 becomes excessive, and the fluctuation of the equivalence ratio of the gas in the cylinder and, consequently, the fluctuation of the engine torque become large.

  On the other hand, in the present embodiment, as described above, when the amount of intake manifold air decreases, a value obtained by subtracting the absolute value of the correction amount G sequentially from the value obtained by adding the basic increase correction amount F to the actual intake manifold equivalent ratio u. Is the target intake manifold equivalent ratio s. Therefore, as shown in FIG. 11, it is possible to appropriately increase the increase in the target intake manifold equivalent ratio s and hence the actual intake manifold equivalent ratio u from becoming excessive after time t3. Therefore, it is possible to suppress an increase in the fluctuation of the equivalence ratio of the gas in the cylinder and the fluctuation of the engine torque.

  Further, in the present embodiment, the amount of purge fuel introduced into the engine body 1 is increased toward the target maximum purge fuel amount Qpurge_max, and is finally controlled to the target maximum purge fuel amount Qpurge_max. Then, the injection amount of the injector 12 is controlled to a value obtained by subtracting the amount Qpure_r of the purge fuel introduced into the engine body 1 from the cylinder required fuel amount Qcyl. Here, as described above, the target maximum purge fuel amount Qpurge_max is a value obtained by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl. Therefore, during the execution of the purge, the injection amount of the injector 12 is gradually reduced toward the minimum injection amount Qinj_min, and is finally controlled to the minimum injection amount Qinj_min.

  Therefore, during the execution of the purge, the total amount of fuel introduced into the engine body 1 can be maintained as the cylinder required fuel amount Qcyl and the engine torque can be maintained at an appropriate value, and the injection amount of the injector 12 is set as the minimum injection amount Qinj A large amount of purge fuel (purge fuel for the target maximum purge fuel amount Qpurge_max) can be introduced into the engine main body 1 while securing the controllability of the fuel amount by the injector 12 by securing the linearity characteristic of 12 and the evaporative fuel Leakage to the atmosphere can be suppressed.

(4) Modifications In the above embodiment, the basic increase correction amount F is changed according to the intake air amount, but the basic increase correction amount F may be set to a constant value regardless of the intake air amount. Good. Even in this case, the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio can be appropriately controlled by setting the correction amount G sequentially according to the air change amount ΔQa. However, if the basic increase correction amount F is changed according to the amount of intake air, the intake manifold equivalent ratio can be controlled more reliably by the value according to the amount of intake air.

  In the above embodiment, the injector 12 directly injects fuel into the cylinder 2. However, the injector 12 may inject fuel into the intake passage 30.

1 Engine body 12 injector (fuel injection valve)
Reference Signs List 30 intake air passage 41 fuel tank 42 canister 43 purge pipe (purge passage)
45 Purge valve 100 PCM (control means)

Claims (4)

An evaporative fuel processing apparatus for an engine, comprising: an engine body in which cylinders are formed; an intake passage for introducing intake air into the engine body; and a fuel tank for storing fuel,
A purge passage connected to the intake passage for introducing a purge gas containing evaporated fuel evaporated in the fuel tank into the intake passage;
A purge valve capable of opening and closing the purge passage;
Control means for controlling the purge valve;
The control means
During the execution of the purge for introducing the purge gas into the intake passage, an increase control is performed to control the purge valve so that an intake manifold equivalent ratio, which is an equivalent ratio of gas in the intake passage, increases. Daisei during your implementation, estimates the current intake manifold equivalence ratio, and, after calculating the increase correction amount of the intake manifold equivalent ratio based on the most recent change of the amount of air flowing through the intake passage, the increase A target intake manifold equivalent ratio is calculated by adding a correction amount to the estimated intake manifold equivalent ratio, and the purge valve is controlled such that the intake manifold equivalent ratio becomes the target intake manifold equivalent ratio. Evaporative fuel processor. In the engine evaporative fuel processing system according to claim 1,
The control means adds a sequential correction amount which is increased or decreased according to the latest change amount of the air amount to a basic increase correction amount which is predetermined so as to increase as the air amount flowing through the intake passage increases. An evaporative fuel processing system for an engine, comprising: calculating a fuel amount as the increase correction amount. In the engine evaporative fuel processing system according to claim 2,
The control means sets the successive correction amount to a value larger than 0 when the latest change amount of the air amount flowing through the intake passage is larger than 0, and the latest change amount of the air amount is smaller than 0 The evaporative fuel processing system for an engine according to claim 1, wherein the sequential correction amount is set to a value smaller than 0. In the evaporative fuel processing system for an engine according to any one of claims 1 to 3,
A fuel injection valve for injecting fuel into the cylinder or the intake passage;
The control means
A reference target fuel amount which is a target value of the total fuel amount supplied to the engine main body based on the operating state of the engine main body is set, and the minimum value of the injection amount of the fuel injection valve concerned to ensure the linearity characteristics of the fuel injection valve Is subtracted from the reference target fuel amount to calculate a target maximum purge fuel amount, and at the time of performing the purge, the amount of evaporated fuel introduced into the engine body via the purge passage reaches the target maximum purge fuel amount And the fuel injection valve is caused to inject fuel in an amount obtained by subtracting the amount of evaporated fuel introduced into the engine body through the purge passage from the reference target fuel amount. Engine fuel processor.

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